Feed modules of this type are normally provided with a sprocket wheel whose radially projecting pins engage in feed holes in the tape and which is rotated in defined angular steps in accordance with the separation spacing of the pouches on the tape. The pouches have a defined positional relationship with respect to the feed holes. At the end of the manufacturing process, centering marks having a defined positional relationship with respect to the pins on the sprocket wheel and which are intended to compensate for the production tolerances are applied on the feed modules in the area of the pick-up point. In addition, it is usual after installing the feed module to measure the position of the centering marks on the feed module in a feed zone of an automatic component mounting machine by means of a camera located on a traveling component mounting head in order to be able to compensate for the installation tolerances. In this situation, operational deviations in the drive system of the feed module cannot be fully eliminated.
As modern technologies have developed, an ever greater level of miniaturization has become a feature of the components to be mounted. It is normal to provide the mounting head with a suction gripping device which is placed over the components to be picked up and which attaches these by suction to its front. In this situation, the gripping device must dip into the pouch in order to be able to come into contact with the component. The permissible tolerances between the feed hole and the pouch are so great that the suction gripping device carrying out the pick-up operation cannot reliably be set up accurately for the component to be picked up and comes into contact with the edge of the pouch and thereby fails to collect the component. In this situation, however, at least over a fairly long section of the tape this is a case of a systematic fault.
The feed mechanisms are designed such that they can for example be operated in accordance with EP 0 589 275 A1 with different separation spacings, whereby a drive motor performs a different number of rotations per advance step before the drive shaft is transported against a rotation stop. Depending on the length of the components, the central position of the component pouch can vary in the pick-up position within a pick-up area. This deviation is taken into consideration by means of an appropriate correction in the position of the mounting head.
According to WO98/37744 A1, for example, it is furthermore normal to arrange a positioning arm for guiding the mounting head in such a way that it extends in the direction of the series of feed mechanisms which are arranged side by side. When the different components are picked from the individual feed mechanisms, the positioning arm must then execute corresponding correction steps depending on the position of the components to be picked up.
According to U.S. Pat. No. 6,032,845 A, a feed mechanism is furthermore provided with a tape drive whose advance distance can be adjusted depending on the separation spacing of the components on the tape. This is driven by a transport wheel with radially projecting pins which engage in the feed holes in the tape. An optical sensor is directed onto the teeth and can thus monitor the precise functional setting of one of the teeth.
In addition, a modular feed mechanism has become known as a result of EP 0345061 A, in which the component tape can be advanced by means of a slider with retractable transport pins. The length of stroke of the slider, which is driven by a compressed-air cylinder, and thus the advance distance of the tape can be set manually by means of an adjustable stop to the relevant spacing division for the tape. Such a change of setting is necessary whenever a tape having a different spacing division is mounted.